


Brotherly Love

by Tsaiko



Category: Undertale (Video Game)
Genre: Accidental Voyeurism, Alternate Universe - College/University, Alternate Universe - Underfell (Undertale), Brother/Brother Incest, Explicit Language, Fellcest - Freeform, Fontcest, Incest, Just a bit too much, M/M, Masturbation, Multi, Pre-Relationship, Pre-Slash, Puns & Word Play, Red loves his brother, Self-Hatred, Sibling Incest, Underfell Papyrus (Undertale), Underfell Sans (Undertale), Unrequited Love
Language: English
Status: Completed
Published: 2020-05-09
Updated: 2020-05-09
Packaged: 2021-03-03 01:34:46
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,685
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24096652
Author URL: https://archiveofourown.org/users/Tsaiko/pseuds/Tsaiko
Summary: Red was quickly coming to the conclusion that there was no good way to ask someone if they were fucking their brother.He also learned that asking questions, even if just in your mind, was a good way to prompt the universe to answer them. Immediately. In graphic detail.
Relationships: Papyrus/Sans (Undertale)
Comments: 9
Kudos: 80





	Brotherly Love

**Author's Note:**

> The internet is for porn.  
> The internet is for porn.  
> Why you think the net was born?  
> Porn. Porn. Porn.
> 
> This is one of the many ideas I considered for the University AU series ([Art Imitates Life](https://archiveofourown.org/works/21961189) is set in the same universe). I ultimately decided not to go this route, but the first line of the fic would not leave me alone. It was just too good to not use.

Red was quickly coming to the conclusion that there was no good way to ask someone if they were fucking their brother.

Was it a little odd to come to that conclusion in the basement of said brothers while waiting for his laundry to dry? Possibly. But fuck it, Red's life was more than a little odd already, and it could stay as odd as it liked as long as it included private access to a washer and dryer. Their own shithole apartment didn't even have laundry facilities and Red and Edge had become all too familiar with how much using a laundromat once a week sucked. 

He was pretty sure Sans and Papyrus – this Sans and Papyrus, as if that wasn't a mindfuck all its own – had more than brotherly feelings for each other. Like 100% sure. Maybe 90%. But that wasn't enough for Red to say anything. Red had more than brotherly feelings for his brother and he'd spent the last seven years of his life keeping those feelings locked down tighter than the safe at Grillby's. Just because he was sure those two had feelings for each other didn't mean they were acting on them.

If he was going to ask someone if they were boning (heh) their brother, then he was damn well going to be sure that's what was happening. Just knowing about "feelings" wasn’t going to cut it. If Red asked, and he was wrong, then there was the whole having to explain why he thought Sans and Papyrus were sleeping together. Stating shit like that when you weren't sure was a good way to get yourself killed. Or worse, lose Edge the only two friends he'd made since they'd come to the surface. 

Fuck that. Edge had given up so much for him already. Red was damned if his brother was going to give up any more.

His generosity towards his brother did not extend to folding laundry. The dryer dinged and Red just dumped everything, still warm, into the basket. It smelled off: Papyrus bought a different detergent than Edge did and they had actual dryer sheets too. Red wasn't going to pass up not having to wrestle with clingy sheets. The clothes were clean. That was what mattered.

He had to hand it to Sans and Papyrus, they had a nice washer and dryer. Not top of the line, but Papyrus was not going to stand for one of those crappy stacked models that could do maybe two pairs of jeans and a T-shirt. No. These babies were big enough to wash an entire week's worth of clothes in. Red would know.

For a moment, Red just stared at the clothing, lost in thought. The smart thing to do was just ignore the whole situation. Sans ignored the times Red fucked up and let his true feelings show. He was a good actor, but even Red knew he couldn't keep up a con 24/7. And that fucker could read him just as easily as Red could read others. He noticed the way Sans would sometimes give him a thoughtful look when Red would let his gaze linger on Edge a little too long, or when his expression grew a little too fond. Bastard hadn't said anything. Just let it ride. Red should really do the same.

The problem was that the situation was an emotional wound that had scabbed over but still ached. Red kept picking at it. He wanted to be horrified. Hell, Red was horrified. He'd managed to keep his dick in his pants when it came to his brother. Sans should have had the decency to do the same.

How did this supposedly nicer, more decent version of himself get what Red couldn't have?

Which was not the way Red wanted to think about it.

Instead of thinking, Red picked up the laundry basket. It was tempting to take a nap in the pile of warm clean clothing. That was Red's favorite way of dealing with problems. Take a nap and hope they went away on their own. He'd learned long ago that never worked. Staying still, ignoring the problem, and hoping it went away just gave the world time to take a dump on you.

Red froze at the sound of footsteps in the kitchen. His fingers tightened on the handle. Someone was there. Someone might see him. His breath felt trapped in his lungs as Red moved the laundry behind the shelves in the corner. It was dark and smelled faintly of musty paper. Somehow managed to squeeze himself in with his back against the concrete wall and the laundry in front of him. Red could feel sweat starting to bead on his skull.

Only when he was wedged into the corner in the dark did Red take a shaky breath. This wasn't the Underground. They were on the surface. No one was going to come after him and his brother. Red gave a humorless laugh. Look at him. Once he'd been the terror of the Underground. 

Stupid instincts. Papyrus had told him and Edge that they were welcome to use their washer and dryer. There was no reason to hide. Red hadn't done anything wrong. Sure, Papyrus probably intended for Red to come in through the front door and not take a shortcut in, but they hadn't complained so far. And Red was sure they'd noticed the increase in detergent usage. If they had a problem, they would have said something by now.

All the reasoning in the world didn't stop Red from pressing back against the concrete walls as someone opened the basement door. He managed to still his shaking bones. Stay quiet. Stay still. Don't attract attention. Strike to kill if you have to fight. Five years of relative safety couldn't undo the previous twenty-three years of survival skills. 

There was a grunt and the heavy sound of footsteps. Carefully, Red looked through a crack in shelves. Sans was hauling a laundry basket down the stairs. A large laundry basket. Lazy fucker couldn't even split up the loads. Not that Red enjoyed doing multiple small loads. He just knew clothes lasted longer if you separated them out and washed them according to the label. They couldn’t afford to wear through clothes. Unlike some people who could obviously just dump everything in and buy something else when it got fucked up.

Red watched as Sans started the washer filling and put detergent in the water. He breathed in slowly and out slowly. It was okay. He was okay. It was just fucking Sans.

Now what? Hiding seemed ridiculous now that Red knew it was just Sans. Part of Red was tempted to pop out from behind the shelves just to see his reaction. If he did that, then it wouldn't seem like a weirdo hiding in the basement for no reason. Instead he'd be the weirdo hiding in the basement just to play a prank on Sans.

"SANS?" Red froze and shifted his weight back. Nope. Getting the jump on Sans was a joke. Getting the jump on Papyrus led to him being face down on the floor with a knee in his back. He'd only had to learn that lesson once. Looks like he was going to have to wait until they left before he could leave.

"downstairs. i'm doing laundry." A pause. "want to hear a joke? i got loads of them."

Red couldn't help but grin at the disgusted noise Papyrus made. His voice got louder as he got closer. "THAT'S NOT EVEN A LITTLE BIT FUNNY."

"not funny? well i'd throw in the towel, but then i'd have more laundry to do."

"UGH." 

"no? maybe you need a dryer sense of humor."

Papyrus's footsteps were loud as he stomped down the stairs. "DID YOU REMEMBER TO SEPARATE THE COLORS FROM THE WHITES?" Heh. Red should have known Papyrus wouldn't put up with that shit. He knew better than to dump in everything.

"nope."

"REALLY? DO WE REALLY NEED A REPEAT OF THE PINK SOCKS INCIDENT?" Papyrus sighed. Pink sock incident? Sans must have washed something red with the whites. Red bet dealing with that was _loads_ of trouble. "YOU CAN NEVER GET ALL THE RED OUT EVEN WITH BLEACH."

"i've already put everything in the wash and i'm washing it on cold."

"SANS."

"heh. fine. i'll separate them." Red listened to Sans rummaging through the washer and the sound of wet clothes being returned to the hamper. A quick peak showed Papyrus watching Sans as he worked. "okay bro. all the colors are out."

"THAT WAS A CLOTHES CALL." Sans laughed. Red felt his smile go fond. What was the harm? It wasn't like anyone could see him and call him on his squishy feelings.

Then Papyrus's voice dropped to something low and dangerous. "It's so nice of you to actually listen." A shiver went down Red's spine, closely followed by a pulse of heat through his joints. Holy fucking shit. What the hell? "I should encourage that."

"really." Red knew what he sounded like when he was flirting, and Sans was definitely flirting. With his brother. Wow. He wasn't sure how he felt about that. "how do you plan on doing that?"

There was the sound of metal like something – someone – had just been set up on the dryer. Part of Red, the part that urged him to always be aware of his surroundings, wanted to watch what was going on. Another part was telling him to just stay quiet and undiscovered until this was over. A third part was screaming at him to get the fuck out of there before he learned a lot more than he wanted to know about Sans and Papyrus's "relationship."

Red peeked through the crack in the shelves.

All he could see the back of Papyrus. He was facing the dryer, and though Red couldn't see anything, he was willing to be good G that Sans was sitting on the dryer. There was the soft sound of skeleton kisses, then the absolutely filthy sound of tongues twining together. Sans made a shivery little noise. Red swore he could feel his magic pulse with the sound.

Yep. This is what Red got for staying still. The universe taking a big dump on him. He really should have known better than to ask questions he didn't really want the answer to. Even if he only asked them in his head.

Papyrus's shoulders were moving, like he was running his hands all over Sans. Like Sans was something special. Something precious. Something worthy. Or maybe that was just Red reading more into things than were there.

He closed his eyes, but somehow that was worse. When he couldn't see, all Red had to go on was his imagination. And his imagination just proved that he was a filthy fucker. Every sound Papyrus dragged out of Sans was accompanied by a graphic depiction of what Papyrus might be doing to cause it. Hands and tongues and the rustle of clothing being disturbed. How he touching Sans. 

Red swallowed, pushing himself back against the wall. It was cool to the touch, which helped because his magic felt like it was lava in his veins. He knew he was sweating, could feel it leaving bits of dampness against his clothes. Sans groaned. Magic settled heavy and thick in his pelvis, an ache that was pleasant now but would only get worse the longer Red kept anything from forming.

How far were they going to go? How long would he be forced to listen?

The worst part was Red couldn't even fucking teleport. There was no way to do it silently, and the sound was fucking distinctive. They would know Red had been listening to them. They would _know._

It seemed like a flimsy excuse, even though he knew it wasn't, because Red didn't want to leave. He couldn't have Edge. He wouldn't do that to his brother. But he could at least listen to these two. Red was learning all sorts of things about himself. What kind of pervert did that make him?

"fuck. paps." Red wasn't sure what Papyrus was doing to Sans to make him sound like that. All he could hear was the gentle rasp of bone on bone. He concentrated on keeping his bones from rattling.

"Language." It didn't take a judge to hear the fondness in Papyrus's voice even as he scolded Sans. "You shouldn't be vulgar."

That earned him a laugh. "i shouldn't be vulgar? i'm not the one with my fingers..." Wherever Papyrus's fingers were would have to remain a mystery for the universe, because Sans's voice trailed off into a small, needy sound. Red could imagine where Papyrus's fingers were. Would they be slick with blue from Sans's cunt or with precum from his dick?

"You can't be vulgar if you're busy," Papyrus said. There was a wet sound closely followed by a whimper. The magic in Red's pelvis tried to form something and Red pushed it back. 

"i guess getting busy isn't enough to stop me." Red grit his teeth against the involuntary laugh that wanted to come out. Holy shit, how could Sans make a joke in the middle of this? Red could barely think past the pulse of his magic and he wasn't the one getting touched.

"What..." There was a long pause. "If you can still make jokes, I'm not doing something right." There was a sudden increase in the pitch of Sans's moans. Red swallowed. He didn't know what Papyrus was doing now, but it was definitely right. "You were saying?"

"don't remember. don't stop."

"Don't worry Sans. I don't plan on stopping until you come," Papyrus replied.

Those words were burned into Red's brain. His magic pulsed dully in his joints, and throbbed in the cradle of his pelvis. He could feel his claws digging into his metacarpals, bright points of pain that helped ground him. Red felt like a voyeur. Hell, he was a voyeur. The shame and want curled in his soul only seemed to make things sharper. More real. More intimate.

Sans's breathing sped up as did the slick sounds. Red clenched and unclenched his hands. He didn't know how much more he could take. He didn't know how much more _Sans_ could take. Fucking hell, stamina was not one of their attributes.

"please. papyrus. i can't."

"Come for me, Sans."

Somehow, Red managed to keep quiet as Sans shuddered through his orgasm. Fuck. The sounds he made – desperate, breathy noises – were going to haunt Red. His soul squeezed until tears formed in the corners of his eyes. 

There was a long pause broken only by Sans's unsteady breathing and the sounds of the washer beginning the spin cycle. It was such a normal every day sound. Red's world had been turned upside down in the time it took for a washer to fill. He would have laughed if it could have.

When the silence continued, Red dared to open his eyes. The corner was still dark. The wall was still cool behind him. How dare the world seem so normal now? He looked through the shelves. Red could see Papyrus's back, relaxed and still in a way Papyrus rarely was. His arms were around Sans. Staying with him. 

Finally, Sans breathing evened out. He began to shift in Papyrus's arms. "looks like i made a mess of my shorts."

"THEN IT'S A GOOD THING YOU ARE ALREADY DOING LAUNDRY, NYEH NYEH," Papyrus replied. Red watched Papyrus nuzzle Sans's head in obvious affection. Red closed his eyes again. He shouldn't be watching this. He didn't deserve to watch this. "WHEN YOU ARE DONE, COME UPSTAIRS."

"upstairs?"

He couldn't hear what Papyrus whispered in Sans's ear about why he should come upstairs when he was done with the laundry, but he could hear the whimper Sans made in response. Red wished they would just go already. His magic hurt. All he wanted to do was let it form and get off.

The sound of Papyrus's footsteps going up the stairs was like music to Red's ears. He dared to look. Sans had shucked his shorts off. Blue stained the inside of his femurs, clear evidence of just what he and Papyrus had been doing. The shorts were tossed into the laundry basket with the other colors. Then Sans was heading up the stairs faster than Red had ever seen him move before.

Five seconds passed. Then ten. Then twenty. Red silently counted them until he hit sixty. Only then did he grab the laundry basket and step into the void.

The sun coming through the window in his room seemed weirdly bright after the dimness of the laundry room. Red dropped the laundry basket. His magic snapped into place in his pelvis and flooded his mouth. It was a relief to stop fighting, to just let his body do what it had wanted to do since Sans and Papyrus started flirting. He didn't even try to fight it. Just kicked off his shoes and flopped face down on the sheets of his bed.

His fingers found the folds of his cunt already slick. The angle was wrong though. Too much strain on his wrist. Rather than roll over, Red pushed his shorts down to give himself easier access.

One finger went in easily. So did two. A third finger brought on the slight burn of being overstretched. Red shuddered, pushing in just to feel the discomfort. It helped push what he was feeling right up to the edge (heh) of too much.

Would Papyrus (Edge) watch him touch himself? Or would Papyrus (Edge) do it to Red? Red couldn't imagine either of them wanting him to go fast. They'd go slow, teasing him, drawing it out the same way Papyrus took his time with Sans. He pulled out a finger, leaving two inside him to slide through the wetness.

_It's so nice of you to actually listen._

It didn't seem to matter to his libido that the voice in his head was Papyrus, and not his brother. Red pulled his pillow to him and bit down. This was going to get loud. And messy. 

He released some of his tension, letting his bone rattle. Slow. Red scissored his fingers to open himself up. His breath came in little huffs from his nasal aperture. It wasn't enough. Red pulled his fingers out and touched his clit. The little nub was slippery with his own slick.

_I should encourage that._

Normally, Red would go hard and fast. Now he touched his clit slow. Teasing himself. His breath hissed out between his teeth. It felt good, but not in the way it normally did. Too gentle. He needed a little pain to keep him grounded, but that's not what he wanted. That's not what he imagined Papyrus (Edge) would want.

Pleasure built but then leveled off. It wasn't enough. Red groaned in frustration and pushed his finger back in him. He wanted the stretch. He wanted to feel full, to have something to clench around. That alone wasn't enough to get him off though.

_The noises Sans had made, choked off little groans and whimpers. The wet sounds of them kissing, tongues and teeth. Papyrus's hands down Sans's pants. Feeling how wet Sans was for him._

Red shifted his hips again, twisting his hand. He still had his fingers in him though not as deeply as before. This angle allowed him to grind his clit against the bones in his hand. He moaned. His hips pressed down, frantically chasing the feeling. Humping the bed. It felt good. Magic burned in his joints. 

He could feel the pleasure beginning to rise again. It wouldn't be long. Not like this. Red realized he sounded like Sans. Was this what Sans felt like when Papyrus touched him? This burning need to keep moving? To chase the pleasure for his brother's sake?

_I don't plan on stopping until you come._

Something in Red snapped. His hips set a brutal pace, fucking his fingers and grinding against the mattress. He wasn't going to last long. His orgasm was rising up, a tension that threatened to drag him under without mercy. It was already building in his back, in the way his femurs trembled, in the ache in his wrist. 

"Paps..." The word came out without conscious though. Saying it out loud made it more real. Red burned with shame, even as his orgasm crested. "Please."

When Red heard Papyrus's voice in his head this time, it was raspier. Deeper. It sounded like his brother. _Come for me, Sans._

The orgasm hit him like a physical blow. Red had enough presence of mind to bury his face in his pillow and muffle his shout. His cunt clenched around his fingers, tight enough that Red could feel it. It went on and on. Just when he thought the wracking waves were receding, they'd grab hold of him again and shake him like a rag doll. Red continued to grind his clit against the side of his hand until it grew too sensitive and his hips twitched away against his will. Even then, sweaty and oversensitive, he didn't want to stop. Fuck. Fuck. _Fuck._

His sense returned slowly as his breath calmed. He felt sticky and gross, and the air in his room was too cold. Red winced as he pulled out his fingers. How did something feel so good going in and so not going out? He didn't know. There was a rip in his pillow case from his teeth. Magic from his mouth had left faint pinkish stains on it.

Slowly, Red held his head up to examine the damage. His fingers were tacky with his own cum. His shorts were damp and his sheets were stained red. Even as he looked at the mess, Red felt a trickle of slickness slide down his femurs. He let his head drop back down and rolled out of the wet spot.

Fuck. Red needed to do laundry again.

**Author's Note:**

> Sans 100% realized Red had been using their washer/dryer. The dryer was still warm when Papyrus sat him on it. He just didn't realize that Red was still there when he and his brother were getting down and dirty. Oops?
> 
> My original plan was for this to lead to a foursome between Papyrus, Edge, Sans, and Red. I can still see it going that way. I just don't know if I'll write anything past this first chapter. I mean, it's hard to top (ha!) a scenario like the one in this fic.


End file.
